In U.S. Pat. No. 4,808,256 an apparatus is described for sealing an envelope on a tire as it is being recapped with precured tread rubber. Generally, the apparatus comprises a pair of separate and identical clamping devices that seal the side edges of an annular envelope on the beads of the tire being recapped. The tire casing is first prepared for recapping in the usual manner by first buffing its tread area and then applying a thin layer of uncured cushion gum rubber, over which a precured tread rubber strip is applied and stapled in place. The envelope fits over the tread rubber and must be sealed around the tire bead areas by the clamps so that no air can be trapped between the envelope and the outer surface of the tread rubber and possibly migrate under the tread rubber during a tire retreading procedure.
Each clamping device describe in the aforesaid patent comprises an outer pressure ring sized to fit against the outer bead area of the tire and a series of backup pads adapted to bear against the inside bead area of the tire. A linkage between the pressure ring and the backup pads and controlled by a handle, operates to move the ring towards the pads to grip the tire bead and seal the envelope to it before the tire assembly is placed in a heated pressure chamber during a recapping cycle.
When the pressure ring and backup plates are moved by the linkage against the outer and inner sides of the tire bead, their relative travel from an opening to a closing position must be such that ample sealing pressure is applied by the ring. Since tires of different sizes have bead sections of varying thicknesses, it is necessary that the distance between the pressure ring and backup plates in the closed position be adjustable in order for the clamping apparatus to accommodate a range of different tire sizes.
A general object of the present invention is to solve the aforesaid adjustment problem for a clamping apparatus similar to the one described in U.S. Pat. No. 4,808,256.
A general object of the present invention is to provide an adjustment tire retreading apparatus that will accommodate tires of different bead thicknesses wherein the adjustment mechanism is controlled by a single rotatable element.
Another object of the invention is to provide a clamping device comprising a compression ring and a series of backup pads integrated by linkage having a single handle and an adjustment means in the linkage for changing the distance closed in order to accommodate tires having different bead between the ring and the pads when the clamping device is thicknesses.
Still another object of the invention is to provide an adjustable tire retreading apparatus for sealing an envelope on a tire casing during a retreading process, and one that is easy to operate as well as being well adapted for ease and economy of manufacture.